JSF datatable: adding and removing rows clear rows values - jsf

Question

I have a h:datatable showing a list of rows, and the fields of each row are input fields.
I render an "Add Row" button before the table, and a "Remove Row" button on each row of the table.
The baking bean is viewScoped, and the buttons add/remove elements from the java list in the backing bean, and then return to the same view.
I set the immediate attribute to "true" in the buttons in order to not validate the input fields when I add or remove a row.
Everything works ok but one thing: the values of the input fileds are cleared. I thought that the view kept the values beacuse the bean is viewScoped.
How can I achieve adding/removing rows without triggering validations and keeping the values that were already typed by the user in the form?
My view:
<h:form>
<h:commandButton value="Añadir Fila" immediate="true" action="#{tablaController.addRowAction}" />
<h:dataTable value="#{tablaController.lista}" var="fila" cellpadding="0" cellspacing="0" border="1">
<f:facet name="header">TABLA</f:facet>
<h:column>
<f:facet name="header"><h:outputLabel value="NOMBRE" /></f:facet>
<h:inputText id="nom" value="#{fila.nombre}" />
<h:message for="nom" class="msjError" />
</h:column>
<h:column>
<f:facet name="header"></f:facet>
<h:commandButton value="Quitar Fila" immediate="true" action="#{tablaController.removeRowAction(fila)}" />
</h:column>
</h:dataTable>
</h:form>
My backing bean:
#ManagedBean(name="tablaController")
#ViewScoped
public class TablaController {
private List<Fila> lista;
...
public TablaController() { }
...
#PostConstruct
public void init() {
this.lista = new ArrayList<Fila>();
for (int i=0; i<5; i++) {
Fila fila = new Fila();
fila.setNombre("");
this.lista.add(i,fila);
}
}
...
public String addRowAction () {
Fila fila = new Fila();
fila.setNombre("");
this.lista.add(fila);
return "";
}
public String removeRowAction (Fila f) {
boolean exito = this.lista.remove(f);
return "";
}
...
}
UPDATE --> MY SOLUTION:
I write here my solution if someone is interested.
The problem is that I use immediate="true" to skip validations, but this makes to skip the update_model_values too, so that the values entered by the user in the form are lost after clicking the add/remove buttons and re-redenring the page.
As I use "JSR-303 bean validation", my solution was to skip validations using the f:validateBean to enable/disable them. Depending on the button I click, if I want the validations to execute, I enable the bean validation (for example in a "submit" button), and if I want to skip them, I disable bean validation (like in the add/remove row buttons). But anyway the update_model_values always executes, so the values are not lost.
Here's the view:
<h:form>
<f:validateBean disabled="#{!empty param['disableValidation']}">
<h:commandButton value="Añadir Fila" action="#{tablaController.addRowAction}">
<f:param name="disableValidation" value="true" />
</h:commandButton>
<h:dataTable value="#{tablaController.lista}" var="fila" cellpadding="0" cellspacing="0" border="1">
<f:facet name="header">TABLA</f:facet>
<h:column>
<f:facet name="header"><h:outputLabel value="NOMBRE" /></f:facet>
<h:inputText id="nom" value="#{fila.nombre}" />
<h:message for="nom" class="msjError" />
</h:column>
<h:column>
<f:facet name="header"></f:facet>
<h:commandButton value="Quitar Fila" action="#{tablaController.removeRowAction(fila)}">
<f:param name="disableValidation" value="true" />
</h:commandButton>
</h:column>
</h:dataTable>
<h:commandButton value="Submit" action="#{tablaController.saveData}" />
</f:validateBean>
</h:form>
The backing bean:
#ManagedBean(name="tablaController")
#ViewScoped
public class TablaController {
private List<Fila> lista;
...
public TablaController() { }
...
#PostConstruct
public void init() {
this.lista = new ArrayList<Fila>();
for (int i=0; i<5; i++) {
Fila fila = new Fila();
fila.setNombre("fila "+i);
this.lista.add(i,fila);
}
}
...
public String addRowAction () {
Fila fila = new Fila();
fila.setNombre("");
this.lista.add(fila);
return "";
}
public String removeRowAction (Fila f) {
this.lista.remove(f);
return "";
}
...
public String saveData () {
...
//processes the valid data
//for example, calls to a service method to store them in a database
...
return "";
}
...
}

Answer 1

I set the immediate attribute to "true" in the buttons in order to not validate the input fields when I add or remove a row.
immediate="true" is the wrong tool for the job. It should be used to prioritize validation, not to enable/disable validation. The difference is rather huge as you encountered yourself.
You want to trigger validation conditionally. In case of e.g. required="true" that'd be as easy as
<h:inputText ... required="#{saveButtonPressed}" />
where #{saveButtonPressed} evaluates true when the save button is pressed. E.g. when its client ID is present in request parameter map.
In case of JSR 303 bean validation, that'd be a matter of
<f:validateBean disabled="#{not saveButtonPressed}">
<h:inputText ... />
</f:validateBean>
or with OmniFaces <o:validateBean> which allows controlling that on a per-command basis.
<h:commandButton id="add" ...>
<o:validateBean disabled="true" />
</h:commandButton>

Answer 2

I had exactly the same problem. In short, you can NOT use immediate for action that update data table(UIData) or facelet repeat. Short explanation:submitted values are not kept for re-display if inputs in UIData do not go through validation. Long explanation can be found here: long explanation and a related bug in Mojarra